The parts of an autopilot (A/P) system, include:
- the computing unit, or brain
- a control head, but some MFDs can be used without a dedicated control unit. Experienced A/P users will usually recommend a dedicated control head, in addition to the MFD interface.
- the hydraulic pump
- hydraulic hoses - usually three - connecting the three ports on the hydraulic pump to the two sides and center of the helm pump.
- a feedback system at the engines, unless "virtual feedback" is being used. Note: Virtual feedback usually works quite well, as long as you have a tight hydraulic system.
- electrical power to the computing unit, which in turn provides power to the pump, so some wiring to do.
- a heading sensor to not only tell the system exactly what the heading is, but also provide the rate of turn. These can be a PITA to initially calibrate and keep calibrated - better options are available but cost $$$.
- an information system, or bus, to allow all these devices to talk to each other. This is now almost always NMEA 2000, and you don't indicate if you have that set up or not.
I installed three different systems on our Islander over the years, plus parts replacements and upgrades. Have also installed complete systems for about half a dozen folks. It isn't too difficult if you are mechanically and electrically adept.
You indicate getting a Garmin discount, but don't say whether this A/P purchase will include new MFDs or do you hope to interface older MFDs to the newer equipment? Success with this will depend on the age and capabilities of the older equipment. I will say that if your current MFDs are not NMEA 2000 compatible you really should consider some significant upgrades.
Do the ETECs have NMEA 2000 data output? If so, your NMEA 2000 bus and interfaces should be entended aft to include the engines, as much good info may be available.
I have digressed a good bit from your original query, but only because you didn't provide much background info.
Best of luck.
Brian
